Urban sprawl (low-density development, unlimited outward expansion) is associated with obesity risk in adults. The objective of this proposal is to determine whether improvements in neighborhood design are associated with changes in activity and weight over time. We will investigate these issues in 2,405 women aged 65-92 years who lived in Portland, Oregon, and participated in the Study of Osteoporotic Fracture in women longitudinal cohort study. Portland, a mid-sized city in the Northwest, provides a unique setting in which to test hypotheses regarding the causal role of local neighborhood design in influencing health and health behaviors. Regional policies to limit sprawl and encourage redevelopment in designated urban centers and transit corridors led to improvements in several key indicators of neighborhood design associated with walkability during the 1990s. Disaggregated and objective data characterizing each woman's local neighborhood design will be linked in historical time to this existing cohort, for whom physical activity and measured body size was assessed at multiple time points. We will quantify the association between changes in neighborhood design characteristics and changes in walking and body size in these older women. Further, we will evaluate whether these associations are modified by individual characteristics of the women, including length of neighborhood residence, socioeconomic status, and physical function. By focusing on specific neighborhood design characteristics, we move beyond dichotomous classifications of neighborhoods (sprawl vs. no sprawl) to determine the impact of specific policy-relevant neighborhood measures on health. This project combines perspectives from urban planning and epidemiology; findings would suggest policy and interventions to prevent obesity among urban-dwelling, normal-healthy, older women. Public health relevance: This proposal addresses an important, new question in public health -- how does the built environment affect physical activity and obesity? -- by examining how differences and changes in neighborhood design elements over a 10-year period affect walking and body size among older women in Portland, Oregon. Findings would suggest policy and interventions to prevent obesity.